Securitization Activities - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Net Asset related to Other Continuing Involvement	$ 65	$ 92
Fair value of retained interests	1,880	1,160
Other Retained Interests [Member]
Fair value of retained interests	$ 61	$ 44
Weighted average life (years)	3 years 7 months 6 days	3 years 6 months
Maximum Exposure to Adverse Changes in the value of retained interests relating to Other securities	$ 61	$ 44